The choice

I'm not exactly sure how many different rifle calibres exist but know enough to know there is a lot. There's people out there who make it their business to know about all of them, I just don't have that much time in my day so focus on those relevant to me. Depending what type of shooting I'm doing and what I'm killing, the calibre changes so over the years have worked with a wide variety of calibres but, as stated above, have focused only on those that are specifically pertinent to me and the situations I am in and I find no joy in talking about rifle calibres endlessly, I prefer to be shooting them.

I have done a lot of hunting over the thirty three years I've been shooting and a lot of other types of in-the-field shooting as well, but in this post I'm referring only to hunting-suitable calibres although they're interchangeable at times.

Calibres have names like 17HMR, 221 Remington Fireball, 22-250 Ackley Improved, 6.5mmx55 Swedish Mauser, 7mm WSM, 465 Nitro Express, 7.62x54R Russian and 30-40 Krag among others, and are as individual in nature and use as the names they have. Sure, they all essentially do the same thing; that is, get loaded into a rifle and sent downrange, but their purposes are vastly different and they've been developed for specific uses and applications.

To further complicate matters, different projectiles can be inserted so each calibre has multiple applications and then to further complicate things again, different gunpowder's can be used, each with various individual characteristics, and so for each calibre there's so many variations it can make the head spin. There's about one hundred and sixty hunting-suitable calibres and between them hundreds and hundreds of different combinations - Thousands probably.

Getting back to basics, the right calibre must be selected for the purpose at hand.

Bullets, (projectiles) don't necessarily do the killing; a projectile is simply a delivery system for energy, and it is the energy imparted into the target that causes it to die. That's why it's important to select the right calibre and projectile for the job at hand. A large calibre full-metal jacketed military round striking an animal is likely to result in a through and through wound but may fail to impart enough energy to kill. Sure, it may hit vitals, but that doesn't always mean a rapid and humane death.

A hunting round (projectile) is (generally) designed to mushroom on impact and it's that larger surface area that helps to impart the energy, and do more damage inside the creature. Just so you know, a lot of military rounds are designed to wound, not kill. A wounded man needs others to tend to him, a MEDEVAC (helicopter) to remove him from the battlefield maybe, and that reduces a unit's effectiveness in combat and puts the aircraft crew and aircraft itself in jeopardy.

Choosing the right calibre and projectile is very important to me when I shoot. I am not one who enjoys killing, I derive no pleasure from it, don't smile when I do it, or celebrate it in any way. It's for that reason I carefully select my calibres, projectiles and, indeed, the firearms itself, with the view to dispatching targets quickly and humanely. I've seen how targets suffer when the wrong calibres are used, or the shooter is not capable of the shot being made, and it's disturbing.

I use calibres across the range for hunting purposes such as 17HMR and 22-250 for small to small-medium sized targets like rabbits, hares and foxes. The .243, 7mm and .308 calibres for medium to medium-large targets and 300 WINMAG for larger targets or those being engaged from great distance.

The selections are made based on the amount of energy in foot-pound ft-lbf that will be imparted into the target. There are other things considered like environmental factors, flight time and so on also.

The above chart is generated from my ballistics solver based on many different factors I've put into it like rifle twist-rate and barrel length, scope height, ammunition details, muzzle speed, wind direction and speed, temperature, humidity and altitude calculated into a density altitude reading, the bullet drag model plus a lot more. This is done for each situation and as the environmental conditions change it needs re-doing as the data will also change.

You can see the energy reading in the third column from the left and how it reduces the more distance the bullet flies. You can also see where the projectile goes transonic - below the speed of sound - and all are considered before taking a shot, especially at long range. It's not just a point and shoot thing when the range gets further and further out there.

Calibre selection is critical to making effective shots, that means accurate and humanely; they also need to be repeatable and not fluke shots. I mean for me of course, others do it differently; I'm just not inclined to see something suffer and so make sure I do the work ahead of time reducing the chance of that. I've heard a lot of people talk about guessing shots, using Kentucky windage and the like, and that's all good and well, but I'm more of a one-bullet-one-kill sort of hunter and don't like leaving things to chance so choose my calibres, and the other factors around making quality shots, carefully.